Diptrace, 4 layer, blind vias

Erik Friesen

I an getting ready to send off a new board, and have not done one that uses blind via's before. I am a little unclear on how diptrace, or other programs for that matter, deal with the drill files.

Is this a matter of the board house?

As shown in my example, there are really only three drill layers, and yet diptrace exports four, one for each layer. Does a board house look at each sandwich to determine which of the three layers gets drilled, or what?

Leon

Why do you need blind vias? They are very expensive.

You have four copper layers, you need a drill file for each one.

Erik Friesen

What do you mean, 3 layer board? What I have shown above is a four layer.

I could rework it with some trouble to get around blind vias, I have a fairly tight layout. Is it better to go 6 layers than do blind vias?

Erik Friesen

Ok, so if layer 1 drill is from top to second, 2 is second to third, 3 is third to fourth, what is the fourth?

Ok, its probably obvious, Id rather ask than make a mistake.

Leon

You said it was a board with three drill layers, I thought you meant that it was a three layer board.

A six-layer board will probably be cheaper than a four-layer board with blind vias.

Erik Friesen

Thanks Leon, I'll rework my board a little. Board houses would rather deal with 10mil holes than blind vias, I guess.

What is the difficulty in blind vias? I don't understand the process well enough to really know. Are vias plated before, or after the layers get sandwiched?

Leon

I'm not sure how they make them, but they are expensive so they are only used on very high-end boards. None of the usual low-cost PCB suppliers will do them.

Erik Friesen

http://www.jlc.net/~preid/pcbpro/pcb1.htm

I suppose each layer has to be drilled alone. According to this tutorial, the vias are only plated once, after drilling the sandwiched board.